A. Field of the Invention
The present invention relates to hand tools. More particularly, the invention relates to a hand tool for cutting tubular workpieces such as copper tubing used in plumbing systems which is operated by a pull-cord mechanism and thus does not require an electrical or pneumatic power source.
B. Description of Background Art
Plumbing used for hot and cold water service in most contemporary residences and other buildings employs copper tubing to distribute the water to various sites within the building, including bathrooms, showers, kitchens, laundry rooms, etc. At each such site, an elongated length of copper tubing connected to a source such as a water main or hot water heater must be cut to size and connected by a fitting to a water faucet, shower head, toilet tank, or other such fixture.
The number of individual fixture connections and hence number of tubing cuts which must be made during original construction or retrofitting of a building can be substantial. For example, an average full bathroom with a single sink and shower head requires at least 5 separate tubing cuts, and adding another sink increases the total to 7 cuts. Each additional bathroom adds 5 to 7 cuts, the kitchen adds at least 2 cuts for a sink and another 1 or 2 more cuts for a water purifier.
For residences which include a laundry room and/or one or more additional bathrooms, the number of cuts increases by 2 to 7 for each such additional site. Thus, as a bare minimum, even a very small apartment construction requires cutting at least 7 different lengths of copper tubing. A more typical apartment with 2 full baths, each having a double sink, and a kitchen requires making about 20 separate cuts. Thus, for a 100-unit apartment complex, typical plumbing installations would require making 2,000 or more separate cuts in copper tubing.
A traditional method of cutting copper tubing which is still in use consists of using a standard hacksaw to cut tubing to a length required for connecting the tubing to a faucet or other such fixture. A disadvantage of this method is that it is relatively slow, and typically results in a rough, non-square severed cut edge which can make connecting the cut edge of the tubing to a fixture problematic.
Other prior art methods of cutting copper tubing and similar tubular members employ a device which is clamped to a length of pipe or tubing with a screw clamp arrangement, and rotated multiple times around the circumference of the tubing. The device has a cutting blade which presses against the outer circumferential wall surface of the tubing, eventually severing the tubing to a required length. This method, while achieving cleaner, squarer cuts than a hacksaw is substantially time consuming.
In response to the above-described limitations of prior art tubing cutting methods and apparatus, the present inventor invented and disclosed in U.S. Pat. No. 7,845,080 a tubing cutting apparatus which includes a rotary cutting mechanism that has an open area for receiving a length of tubing and has a cutting head provided with a cutting blade for engaging the tubing. The cutting mechanism is powered by rotary power source such as a hand-held power tool, or by a self-contained drive motor. The apparatus includes a gear system for coupling rotary power from a rotary power source to the cutting mechanism and thereby rotating the cutting head and blade about a length of tubing. One embodiment of the disclosed apparatus includes a clamp comprising a slotted tubular leaf spring which protrudes from a handle case of the apparatus in longitudinal alignment with an open slotted area of the cutting mechanism. The apparatus clampingly engages a length of tubing to be cut by pushing opposed flanged edges of the leaf spring against the length of tubing, thus causing the edges to be pried apart against tension exerted by the spring. The edges than spring back to grip the tubing. This arrangement facilitates use of the apparatus in locations with limited accessability, such as within a space behind a wall board of a structure.
The tubing cutting apparatus disclosed in U.S. Pat. No. 7,845,080 provides other substantial advantages over prior art tubing cutting tools. For example, the tubing cutter apparatus disclosed in U.S. Pat. No. 7,845,080 can be positioned and secured in place on a length of tubing, and used to make a clean, square, accurately located severing cut in the tubing, in a much shorter time than prior art cutting tools which require manual clamping operations. However, the present inventor has perceived the need for another type of tubing cutter apparatus which could be operated by hand power alone.
An apparatus powered by hand would be useful in remote areas which do not have a convenient source of electrical power or pneumatic power supplied by pressurized air. Also, it would be desirable to have a tubing cutter tool which was not electrically powered and could thus be used in hazardous locations containing combustible liquids or vapors without the possibility of an electric spark from a drive motor igniting a fire. Moreover, for some applications, it would be desirable to provide a tool for cutting tubular workpieces in which functions of providing a handle for holding the tool, and a mechanism for firmly gripping a length of tubing which was being cut by the tool, could be combined into a single structure.
It would also be desirable to provide a tubing cutter tool which afforded the capability to a workman to readily adjust the number of rotations of a rotatable cutter head to the minimum number required to sever a length of tubing. Prior art powered tubing cutter tools typically are operated in a mode which causes a cutter head of the tool to rotate more than a minimum number to turns around the circumference of a tube, to ensure that a complete severing cut is made. The additional number of often unneeded turns requires additional valuable time which could be saved by a manually operated tubing cutter tool which a workman could readily operate in a mode in which a cutting head was rotated just a sufficient number of turns to cleanly sever a length of tubing but without any additional time consuming rotations of the cutting head. The foregoing considerations were motivating factors for the present invention.